1. Field of the invention
The invention relates to a transporter for lead frames, comprising:
two rotatable wheels with mutually facing running surfaces for engaging a lead frame between the wheels, and
a frame supporting the wheels.
The invention also relates to an assembly of two such transporters.
2. Description of the Prior Art
The transporters of the type stated in the preamble used according to the prior art for displacing and positioning lead frames are generally very suitable for transporting a particular type of lead frame which can be transported with wheels. The application possibilities of the existing transporters are however limited to this type of lead frame.
The present invention has for its object to provide an improved type of transporter as described above with which lead frames of varying dimensions, in particular width and thickness, can be transported without complex change-overs. In addition, a flexibility is sought such that a lead frame can be removed manually from a transporter in relatively simple manner, for instance in the case of defects.
The present invention provides for this purpose a transporter of the type stated in the preamble, comprising:
an actuating cylinder engaging on at least one wheel for mutual displacement of the wheels.
The actuating cylinder is preferably adapted to exert a biasing force. Lead frames of varying thickness can hereby be displaced and/or positioned by the transporter. Another advantage of the actuating cylinder is that it can be employed to exert the biasing force, this biasing force likewise being variable. Depending on the type of lead frame for transporting, the biasing force exerted on the lead frames can thus be varied in simple manner. It is also possible to move the wheels so far apart with the actuating cylinder that a lead frame can be easily removed or inserted. By coupling the actuating cylinder of a transporter to an intelligent control it is also possible to control the clamping force of wheels and/or moving apart of the wheels by means of chosen variables. The actuating cylinder also renders a mechanical spring element unnecessary. This decreases the susceptibility of the device to wear. The actuating cylinder can also be employed as dynamic spring element, which increases the flexibility of the transporter.
At least one wheel is preferably provided with coupling means for a drive to cause rotation of the wheel. Such coupling means enable simple connection of the unit to an external drive, for instance a drive for a plurality of transporters simultaneously. A less flexible and usually more costly alternative herefor is to provide each transporter with a separate drive. An additional drawback thereof is the problem of synchronization of a plurality of transporters.
In a preferred embodiment the actuating cylinder is integrated into the frame. With this measure the transporter can take a relatively compact form, which is particularly advantageous in the complex devices for processing lead frames. Due to integration of the cylinder the transporter also comprises relatively few protruding parts, which makes the transporter less vulnerable. Such a transporter is moreover found to be relatively inexpensive in production.
In another preferred embodiment at least one of the wheels is connected to a translatable guide rod, and a recess receiving the guide rod is arranged in the frame. The guide rod is herein preferably so long that, at least when wheels are placed practically against each other, it projects relative to the frame. By exerting a force on the guide rod the wheels can thus be moved apart. It is thus possible for instance in a press construction, to cause the wheels to move apart during an incoming ram movement. This is particularly desirable since the function of the transporter is required particularly between two successive operations. It is precisely during performing of a determined process that it is usually undesirable for the transporter to engage a lead frame. Due to the guide rod construction the closing of a press, i.e generally the moment at which the process is carried out, can be mechanically coupled to the moving apart of the wheels of a transporter. Another advantage is that such guide rods can also be manually depressed in simple manner, whereby it becomes possible to move apart the wheels of the transporter manually.
In yet another preferred embodiment, the running surface of at least one of the wheels is provided with a substantially cylinder jacket-like running surface for engaging on a lead frame and a standing edge connects onto this running surface on one side, whereby the minimum mutual distance between the running surfaces of the wheels is bounded. The standing edge of a first wheel will in any case lie against the running surface of the second wheel when the wheels are urged against each other, whereby the running surface of the wheel with standing edge is left clear. The advantage of this construction is that a lead frame can be engaged relatively simply between two wheels when the wheels are urged against each other in simple manner.
The invention also comprises an assembly of two transporters as described above, wherein at least one of the wheels of a first transporter is in at least coupled for fixed rotation to one of the wheels of a second transporter. In a preferred embodiment this fixed rotation coupling is realized in that the coupled wheel of the first transporter is provided with at least one projecting coupling shaft and the coupled wheel of a second transporter is provided with a recess for receiving this coupling shaft. A rigid coupling of two mutually opposite transporters has the advantage that a lead frame will be fed through uniformly between both transporters and there is no danger of a change in orientation of the lead frame during transport.
In a preferred embodiment of the assembly, at least one of the transporters is provided with mounting means for releasable mounting of the transporter on a support element such that the transporter is translatable in the direction parallel to the rotation axis of the wheel. The width of the lead frame for transporting can be adjusted by adjusting the mutual distance between the transporters of the assembly. Lead frames of varying width can thus be transported. It is usually desirable herein that a translation of a first transporter corresponds with a translation in opposing direction of the other transporter, for which purpose are known prior art constructions which can be used. It is thus possible to realize that the transporting axis of lead frames of varying width remains constant.